It is known in the art to use compounds such as allylisothiourea, thiourea, thiosemicarbazide, etc. in photographic silver halide emulsions. These are normally added to the silver halide emulsion prior to digestion. If added after digestion or just prior to coating, they are found to be detrimental because they fog the emulsion when the latter is processed in continuous tone developers, and have low sensitivity response in lithographic developers. The present invention provides compounds which may be added after digestion or just prior to coating, without these detrimental effects.